The present invention relates to the prevention of emissions of atmospheric pollutants from vessels containing molten elemental sulfur, and most particularly from vessels such as sulfur pits associated with Claus plants and the like.
In Claus plants, hydrogen sulfide is converted by oxidation to elemental sulfur, and the elemental sulfur is often temporarily stored in sulfur pits in molten form. If the sulfur pit is open to the atmosphere, then, as the level of molten sulfur in the sulfur pit falls and rises, air is alternately drawn into the pit and displaced to the atmosphere. Unfortunately, as the air is displaced from the sulfur pit, it carries with it hydrogen sulfide, which is produced not only by release of dissolved hydrogen sulfide from the molten sulfur but also by the decomposition of polyhydrogen sulfides dissolved in the molten sulfur.
The atmospheric discharge of hydrogen sulfide from the sulfur pit is, of course, a source of environmental concern, inasmuch as hydrogen sulfide emissions are usually strictly controlled by governmental regulations. One process aimed at solving this problem is disclosed in "Improving Claus Sulfur Degassing Technology" by E. A. Watson et al., NPRA Annual Meeting, Mar. 29-31, 1981. In this process, a catalyst is employed "with strong catalytic effectiveness for hydrogen polysulfide decomposition." Thus, this process aims at decreasing the hydrogen sulfide emissions by catalytically converting the polyhydrogen sulfides to elemental sulfur.
The present invention, however, is directed to a noncatalytic method for preventing pollution emissions from sulfur pits and other vessels in which molten sulfur is stored.
It is a further object to prevent pollution emissions from sulfur pits and the like without resulting in a mere transfer of the pollution problem to a different location.
It is a further object not only to prevent such pollution emissions but to slightly increase the overall sulfur recovery from a Claus plant or other sulfur-producing process in which sulfur is produced by oxidation of hydrogen sulfide.
It is yet another object to provide a method for preventing such pollution emissions without requiring substantial changes in the operation of the Claus plant or other process producing the elemental sulfur introduced into the sulfur pit or other temporary storage vessel.
It is yet another object to provide a process wherein a purge gas is introduced into the sulfur pit or other vessel without discharge of emissions from a vent associated with the sulfur pit or from leaks in the sulfur pit itself, and to subsequently remove the purge gas from the sulfur pit and convert the sulfur components contained therein to recoverable, elemental sulfur.
These and other objects of the invention will become more readily understood in light of the following description and claims, both taken together with the attached drawing.